1. Technical Field
The present invention relates to vehicle wind-noise reduction structures for suppressing wind noise occurring near front pillars.
2. Related Art
A vehicle, such as an automobile, has a front windshield provided at the upper front surface of a vehicle cabin and front pillars provided at the opposite sides of the front windshield in the width direction. The front pillars are inclined rearward together with the front windshield from the lower ends toward the upper ends, and side windows are located to the rear of the front pillars. A cowl extending in the width direction of a vehicle body is disposed at the lower edge of the front windshield. This cowl is used for draining rainwater dripping down from the front windshield to the outside of the vehicle and also for introducing outside air into the vehicle cabin. For instance, see Japanese Unexamined Patent Application Publication No. 8-127365.
The cowl is disposed between the front windshield and a front hood. In recent years, gutter-type cowl panels are mainly used in place of box-type cowl panels. Normally, a cowl panel is manufactured by plastic injection molding and has a cross-sectionally U-shaped or V-shaped gutter directly below the front windshield. The opposite ends of the gutter are located at the inner sides of front fenders in the width direction. The gutter is curved rearward from the center toward the left and right sides so as to conform to the curved lower edge of the front windshield in plan view. For instance, see Japanese Unexamined Patent Application Publication No. 2000-280934.
When an automobile is running, the sounds of the engine, the tires, and the wind become noise for a vehicle occupant and causes reduced comfortability for the vehicle occupant. In particular, wind noise near the front pillars (which will be simply referred to as “wind noise” hereinafter) occurs in areas near the heads of the vehicle occupants at the driver seat and the passenger seat and thus causes a reduced level of comfort in the automobile. Wind noise is produced by air flowing along the front surface of the front windshield and then flowing rearward from the front pillars. Specifically, the air flowing along the front surface of the front windshield becomes a vertical vortex, which flows around toward the center of the vehicle body, immediately after separating from the rear edges of the front pillars and collides with air flowing alongside the front pillars so as to produce wind noise.
The loudness of wind noise has a positive correlation with the amount of air flowing rearward from the front pillars. In an automobile equipped with the above-described cowl panel, the loudness of wind noise increases due to an increase in the amount of air flowing below the front pillars. Specifically, a portion of air flowing along the front surface of the front hood is blown into a gutter space of the cowl panel and subsequently flows through the rear-curving gutter space in the width direction. The air flowing to the opposite widthwise ends of the gutter space changes its direction and flows upward by colliding with the inner side surfaces of the front fenders in the width direction, travels over the front fenders, flows in the width direction along the front surface of the front windshield, and merges with the flow of air flowing below the front pillars. As a result, the amount of air separating from the lower rear edges of the front pillars increases, so that the above-described vertical vortex becomes larger, thus resulting in increased loudness of wind noise.